Implications of Epigenetic Regulation in Congenital Myotonic Dystrophy through Development - Project Summary Congenital myotonic dystrophy (CDM), the most severe form of myotonic dystrophy, causes muscle weakness, breathing problems, and feeding difficulties at birth. During childhood affected individuals experience intellectual impairment and gastrointestinal issues while, in contrast, muscle strength and weakness improve. Muscle symptoms experienced by adults with myotonic dystrophy, including myotonia and fatigue, are not observed until individuals reach adolescence. Individuals with CDM and myotonic dystrophy type 1 (DM1) both exhibit widespread alternative splicing dysregulation due to the sequestration of muscleblind-like (MBNL) proteins by expanded CUG-repeat DMPK RNA. Our Center previously performed RNA sequencing on 43 congenital myotonic dystrophy muscle biopsies from individuals 2 weeks to 16 years of age. We found that the severity of RNA mis- splicing mirrored the triphasic course of muscle symptoms captured clinically; children in early childhood showed improvement in RNA splicing dysregulation that regressed in adolescence. Preliminary data also indicates varying DMPK expression in CDM patients, suggesting DMPK’s potential role in CDM pathophysiology, particularly in infancy. While these observations correlate with the clinical course of CDM, the mechanisms responsible for these dynamic shifts remain unknown. This proposal is designed to further clarify and define the molecular mechanisms responsible for the clinical and molecular progression of CDM. This study will characterize the epigenetic landscape around the DMPK locus in skeletal muscle across CDM development and elucidate how DMPK methylation contributes to CDM. We hypothesize that epigenetic modifiers play a significant role in the unique clinical/molecular pattern we observe in individuals with CDM across development, most specifically in infancy, by serving as a protective mechanism to modulate toxic DMPK expression via changes in methylation. Aim 1 will characterize methylation patterns in matched skeletal muscle and blood samples from CDM children, adult DM1 patients, and controls, analyzing changes across development and disease progression. Aim 2 will assess the role of DMPK methylation using iPSCs and CRISPR-based systems to modulate methylation and MBNL expression, examining the molecular effects in myogenic cells. At the completion of this project, we will have mapped the epigenomic course of CDM disease progression across pediatric development and performed experiments vital to understanding the unique mechanisms that contribute to CDM. This research will enhance understanding of CDM's clinical and molecular progression, identify potential biomarkers for therapeutic trials, and provide insights into targeting DMPK methylation in CDM.
